z/OS consists of many elements and features that work together to provide a continuous, high-volume, high-integrity, highly-secure and stable environment that can support key enterprise workloads and functions. z/OS supports batch and online processing, as well as application and business intelligence workloads. It offers many functions for workload management, I/O and data management, data and storage management, security (including identification, authorization, audit, and encryption), networking (SNA and TCP/IP, including IPv6), problem analysis, Parallel Sysplex, and other facilities.
z/OS elements deliver essential operating system functions and are included in the base of z/OS. z/OS features provide additional operating system functions, and can be ordered with the z/OS base. Some additional function is delivered by separate tools and downloads.